Method of fabricating semiconductive devices and the like



y. 1960 r. VAUGHAN 2,937,124

' I METHOD OF FABRICATING SEMICONDUCTIVE ozvzcss AND THE LIKE Filed Feb.4, 195'? 2 Sheets-Sheet 1 May 17, 1960 R. T VAUGHAN 2,937,124

METHOD OF FABRICATING ssmconnuc'rmz DEVICES AND THE LIKE Filed Feb. 4,1957 2 Sheets-Sheet 2 METHOD OF FABRICATING SEMICONDUCTIVE DEVICES ANDTHE LIKE Robert T. Vaughan, Cheltenham, Pa., assignor to PhilcoCorporation, Philadelphia, Pa., a corporation of Penm sylvaniaApplication February 4, 1957, Serial No. 637,972

7 Claims. (Cl. 204-143) The invention hereinafter described and claimedhas to do with the fabrication ofsolid bodies having predeterminedcharacteristics as to form, thickness, surface condition and the like.While being of broader applicability, the invention is particularlyconcerned with the fabrication of semiconductor diodes, transistors andthe like; and it may be used both in the electrolytic etching of a semi-,conductive body and in the electrolytic plating of electrode elementsthereon.

The present disclosure is a continuation-in-part'of a parent applicationSerial No. 559,695, filed January 17, 1956, and now abandoned, entitledMethod of Fabricating Semiconductive Devices, whichvin turn was acontinuation-in-part of an original parent application Serial No.517,453, filed June 23, 1955, and now Patent No. 2,830,697, and entitledMethod of Etching.

The invention may be considered as an improvement upon the'electrolyticjet-etching and plating methods, described and claimed in the copendingapplication of Tiley and Williams, entitled Semiconductive Devices andMethods for the Fabrication Thereof, Serial No. 472,824, filed December3, 1954. It may also be considered as an improvement over theetch-controlling method and apparatus described and claimed in theapplication of Noyce, entitled Infrared Thickness Control for TransistorBlanks, bearing Serial No. 449,347, and filed August 12, 1954, and nowPatent No. 2,875,141. Said copending applications are assigned to theassignee of the present invention.

According to said method of Tiley and- Williams, an electrolyte liquidis applied to a semiconductor or the like, as a fine jet which carriesan electrical current; and according to said method of Noyce, the jetcarries a beam of light or other wave energy. It is desired that theliquid of the jet will flow off from an impingement area on the blank,in form of a thin, flat, flowing sheet. However, disturbing tendencieshave been encountered. For instance, if the jet stream is too fast, itmay break up and cause breaking up of the light beam therein. If the jetstream is very fine, it tends to cause accumulation of a liquid drop orball, adhering to and gradually growing on the surface of the solid bodyand maintained thereon against the force of gravity; and the developmentof such a ball of liquid tends to interfere with the electrolyticprocesses.

It is therefore a basic object of this invention to control orpreferably to prevent such undue breaking up of the jet and also tocontrol or preventsuch undue accumulation of a ball of jet liquid.

A related object is to insure smooth and uniform configuration of theflowing electrolyte liquid. Particularly in and adjacent the impingementarea it is preferred to providea thin, coherent jet column, directlytransforming itself into an even thinner, coherent, flowing liquidsheet. Controlled forces, in opposition to the forces of liquid cohesionin the electrolyte liquid, are applied according to the presentinvention.

Another object is to provide methods whereby conit States Patent trolledpneumatic forces, such as those of a flow of air or other gas,are'appliedlto a liquid body and thereby to a flow of electrical and/orlight energy which in turn serves to modify th'econfiguration of a solidbody. In particular, aspirating means may be used for such control.

The objects have been achieved by applying certain pneumatic andparticularly aspirating means and forces to an atmosphere surrounding anelectrolytic and/or lightguiding liquid column, adjacent asolid contactarea. The details will be noted from the following description, takentogether with the accompanying drawing, wherein:

Figure 1 is aschematic perspective representation of apparatus foroperation according to the invention; Figure 2 is a detailed view on alarger scale, showing a central part of such apparatus and a certainflow pattern therein, asproduced by comparatively large diameter jets;Figure 3 is a detailed view generally similar to Figure 2, showinghowever the undesirable balling-up condition arising with the use ofextremely fine jets when the present invention is not used; Figure 4 isanother view generally similar to Figure 2 but showing the flow patternof an extremely fine electrolyte jet, produced with the aid of theinvention; and Figure 5 is a schematic, sectional view of a transistorblank treated in accordance with the present invention.

Figure 6 is aschematic cross-sectional elevation of a further embodimentof apparatus for operation in accordance with this invention; Figure 7is a sectional plan view taken along line 7-7 in Figure 6; and Figure 8is an enlarged, schematic, sectional detail view of a transistor blankin process of being precision etched in the apparatus of Figure 6.

Figures 1 to 5 Referring initially to Figure 2, a flat, plane-parallelsemiconductor blank 10 is treatedby two electrolyte liquid jets 11, 12,directed against the two surfaces of the blank in opposite and mutuallyaligned directions and desirably at right angles to the blank, thusproviding mutually opposed jet impingement areas 13 and 14 on the blank.As shown in Figure 5, such treatment is applied to form mutually opposedcavities 15 and 16 on the blank 10, leaving between these cavities onlya thin semi-conductor region 17. Subsequently, the semiconductor device,particularly of the-surface barrier type, can be completed by formingand especially by plating certain electrode elements, not shown herein,in the cavities 15, 16.

In the manufacture of many types of semiconductor devices and mainly inthe manufacture of surface barrier units, it is important to providecertain critical configurations in small plates, blocks or blanks MP ofgermanium or similar materials, and particularly to reduce certainregions 17 of such blanks 1.0 to a very minute and accurately controlledthickness. It is also important to shape the thin region 17 withoutdisturbance of the material therein, particularly on the surfacethereof, and accordingly to avoid all ordinary grinding, machining,rolling and similar operations. These results can be achieved by the useof electrolytic treatments, as disclosed in the application of Tiley andWilliams, but only if the electrolyte liquid, supplied by jets 11, 12 tothe solid 10, flows off smoothly;

Preferably the outfiowing liquid is formed into a thin sheet, as shownin Figure 2. In some cases this can be achieved by means of the fluidjets 11, 12, alone; in such cases the jetstreams can be usedsubstantially in the way in. which. they are used in various otherprocesses and industries,.that is, with adequate kinetic energyremaining. in the liquid, after the impingement at 13, 14, toinsure arapid, lateral flow of the liquid, as a coherent sheet, alongthe'surfaces of the solid body 10. It is important to note, however,that atomization of the liquid, caused for instance by excessive jetvelocity, would tend Patented May 17, 1960- thin sheet of liquid;atomization is therefore to be avoided in processes of the present kind.

"Paradoxicall'y, difficulty has arisen also upon the use of a very finejet 11 or 12; and this presents a serious problem, as the use ofextremely fine jets may otherwise be desirable or even necessary inprocesses of the present kind. The liquid'of such a jet frequently formsa single, small, more or less hemispherical droplet, coaxial with jet 11or 12 in the impingement area 13 or 14, adhering to the solid body It insaid area; and, as liquid continues to be added to the area, by the jet11 or 12, such a droplet grows, until it forms a fairly large drop orball 18, see Figure 3. This occurs whenever the kinetic energy remainingin the liquid is so reduced, upon the impingement at 13, 14, as tobecome insuflicient to overcome the forces of cohesion which tend toform the liquid into a sphere. The figure shows a liquid drop 13 whichadheres to the top or bottom of semiconductor blank 19 and the diameterof which almost equals the width of said blank; and it also shows thatthe diameter of the liquid jet 11 is substantially smaller than thediameter of this liquid drop. It will be realized that the maximum sizeof a liquid drop, overcoming the force of gravity by that of liquidcohesion or surface tension, is fairly small by itself and is usuallylimited to a few millimeters. The point of importance is that thediameter of the jet potentially creating and feeding such a drop, in themethod considered herein, is even smaller than the maximum size of adrop of the same liquid; this jet diameter usually amounts only to afraction of a millimeter.

Eventually, sufficient liquid is accumulated in such a drop 18 to causerunning off of the liquid; that is, the weight of the liquid in the dropultimately overcomes the forces of cohesion, or breaks the surfacetension. Immediately, however, the fine jet 11 causes a new drop toaccumulate, repeating the cycle. 7

With typical jets of aqueous electrolyte liquid, a smooth and thin flowover the solid surface, as shown in Figure 2, can usually be expectedwhen the jet has a comparatively large diameter such as about 9 mils ormore. With the use of jets ranging from this order of magnitude down toabout 3 mils in diameter, the etching fluid frequently balls up,particularly when the jet has a thickness smaller than about mils. Whenjets of 3 mils diameter or less are used, the balling-up occurs almostinvariably.

This tendency is of considerable practical significance, inasmuch as jetstreams of diameters down to about 5 mils are usually required for alletching and plating procedures on a semiconductor or the like, and jetstreams of 5 mils thickness or less are frequently required, mainly forthe precision etching. Incidentally, the typical diameter ofrough-etched pits may range from about 8 mils upward; and aprecision-etched cavity may be about half as wide as the rough-etchedpit.

The apparatus of Figure 1 serves to maintain conditions, in and aroundthe electrolyte flow, which militate against the balling-up tendency,even in the case that extremely fine electrolyte streams are used.

These streams are here shown at 19 and 20 and are formed by smallelectrolyte discharge nozzles 21, 22, facing one another and dischargingagainst the blank 10. The nozzles are respectively fed by conduits 23,24, which are branch extensions of a main conduit 25, comprising meanssuch as a pump 26, for drawing electrolyte 27 from a reservoir 28. Thiselectrolyte may comprise any of a large variety of readily ionizablealkali salts or acids in aqueous solution, when it is desired to etchgermanium or the like. Electric current is applied to the jets 19 and2t? and the wafer by means of a potential source 29, a currentregulating resistor 3%, switch 31 and leads 32 and 33. The electriccircuit is completed by attachment of lead 33 to an electrode 34 whichis disposed within 4 the conduit 25, and attachment of the lead 32 tothe semiconductor 10.

The apparatus as described up to this point is substantiaily similar tothat shown in the Tiley-Williams application; and, as indicated above,such apparatus by itself is adequate for the forming of semiconductivebodies, so long as it is possible to use jets of about 9 mil diameter ormore and to produce cavities 15, 16 and electrodes of correspondinglylarge diameter, on the semiconductor body 14 However, where relativelyclose control of the diameter of the cavities and plated elements isrequired, it is necessary to use extremely fine jets 19, 20, typicallyhaving diameters such as 5 or 3 mils or less.

Therefore the present invention, as shown in Figure 1, uses,additionally, a pair of mutually opposed suction nozzles or aspirators35 and 36, disposed in the plane of the wafer 19, adjacent the jets 19,2t), and connected respectively to branches 37 and 3$ of a conduit 39,the end 49 of which extends into a vacuum tank 41. This tank may bemaintained below atmospheric pressure by a vacuum pump 42 and may alsoserve as an electrolyte trap; liquid 27 may return from this tank to thesupply reservoir 28 by a valve-controlled conduit means 43. Anywell-known electrical circuit means or the like may be used to operatethe pumps 26 and 42; for instance a power source 44 may be connectedwith the motors of said pump by leads 45, 46, 4'7, including a switch48.

In the operation of the apparatus of Figure 1, switch 48 is closed; pump26 forces the etching fluid 27 from reservoir 28 through nozzles 21, 22to direct fine hydraulic jets 19, 29, against the blank 16; and vacuumpump 42 reduces the pressure in tank 41 and aspirator system 35, 36, 37,38, 39, thereby producing an area of low pneumatic pressure in theatmosphere wherein blank 10 is exposed and particularly in the plane ofblank 10, adjacent the impingement areas 13, 14, of jets 19, 20.

The presence of this low pressure area causes a rapid flow of air intothe same, from and through the adjacent portions of the atmosphere; andthese portions include the regions overlying and surrounding saidimpingement and low pressure areas. Thus there results an atmosphericflow pattern on each side of the blank, as shown by arrows in Figure 4;that is, a pattern including an air flow which surrounds and parallelsthe jet 19 or 20, and continues directly as an outward flow over theface of the blank 10.

These atmospheric pressure and flow conditions have been found tomaintain the desired conditions of smooth, uniform and thin, sheet-likeliquid flow and to prevent the undesired balling-up, even in case thatextremely fine jets of 5 or 3 mils diameter or less are used.

All or part of the sheet-like liquid flow may ultimately break up inform of droplets, remotely of the impingement area; and some or all ofthese droplets may be drawn into the aspirators 35 and 36. However, itis also possible to perform the present method in such a way that all orpart of the liquid follows a trajectory different from the path of theaspirated air, as will hereinafter be described with respect to Figure8.

When the essential conditions as described above have been established,the switch 31 is closed to energize the electrolytic circuit, which maypresently be assumed to be an etching circuit. It uses the thin jetstreams 1), 20, as conductors, carrying an etching current to thesemiconductor surface to be provided with cavities 15, 16.

It is believed to be unnecessary at the present point to discuss indetail the potentials and other characteristics prevailing in thedifferent portions of the semiconductor etching circuit, such mattersbeing fully discussed for instance in the Tiley-Williams applicationmentioned above. However, it is important to note what would happen ifthe aspirating operation were interrupted during the electrolytictreatment: the resulting formation of a liquid ball 18 (Figure 3) woulddistribute the electrolytic current over the entire area of adhesion ofthis drop to the solid body 16, dissipating the current and causingexcessively wide and flat etching.

If and when this balling-tip is overcome, and the condition of .Figure 4established, this dissipation of current is effectively prevented. Thereason is that any current to be dissipated must now flow outwardlythrough an extremely thin and very resistive sheet or film of liquid,extending along the semiconductor surface. The

maximum thickness of this outwardly flowing sheet of liquid, preventedfrom coalescing into a drop, is usually kept to one quarter of the jetdiameter, that is, usually only about 1 mil or less, by the inherenthydraulic behavior of the jet. The ohmic resistance of such a thin sheetof liquid is too great to allow any substantial spreading of thecurrent, outwardly from the jet column.

For the purpose of plating electrode elements on the surfaces oftransistor cavities 15, '16 suitable method adjustments can be applied,as described in the Tiley-Williams application. Such adjustments mayinclude a reversal of the polarity of the electrolytic circuit, by meansof well-known apparatus, not shown herein. The control over theconfiguration of the flow can be substantially similar to that used asin the etching process, described above.

From one viewpoint the process of this invention can be described asproviding a static, outward, pneumatic pressure drop or gradient,maintained over the impingement area and effective to distort, flattenand destroy a liquid ball inadvertently formed or beginning to be formedFigures 6 to 8 Reference is now made to Figures 6 and 7, whichillustrate means for operation according to this invention for theprecision etching of a semiconductive body, pursuant to a preliminary orcoarse etching treatment which'has produced a body of the form shown inFigure 5.

The body 10 is accordingly shown as having preformed cavities on bothsides and as being further exposed to a single, vertical, upward jet 50,issuing from a jet nozzle 51 and leading to a center part of the lowercavity. This jet is suitably supplied with electrolyte by a conduit 52having an electrode 53 mounted therein; and an etching circuit isestablished, leading from a source of potential, not shown in thisfigure, through a conductor 54, electrode 53, jet 50, blank 10, holder55 and another conductor 56 leading back to the source.

Liquid is withdrawn from the impingement area by aspirator means,generally shown at 57. The entire process is performed in a housing 58,in order to avoid fluctuations of the jet 50 resulting fromanyatmo'sph'eric drafts or the like. Advantageously, the blank 10 andholder 56 are oriented relative to the jet nozzle 51 by guide means 59,cooperating with a wall of the housing 58. Opposite this guide means asuction head or conduit 60, forming part of the aspirator system 57,enters the chamber'58; and within this chamber a plurality of suctionnozzles 61, 62, 63, suitably connected with the header, are distributedaround the jet 50, in or slightly below the plane of the blank 10. Ihave found it preferable to employ two, three or more nozzles 61, etc.withfiat intake openings, machined of metal, and to regularly distributethe nozzles and their suction areas around the jet, while orienting themin an accurately spaced, parallel relationship with respect to the blank10. The housing 58 is desirably made of glass or the like, in order tomake it possible to observe the operation within.

For the control of the precision etching of germanium I preferablyemploy infrared light, as disclosed in the 6 Noyce application, whereasother light is equivalent or preferable when etchingsilicon or the like.Accordingly I provide a beam 64 of suitable light or otherelectromagnetic radiation; and such light may enter the apparatusthrough a transparent plastic cone 65, forming a raised bottom part ofthe jet-nozzle 51 positioned as close to the nozzle discharge apertureas possible. From here the light may pass upwardly, coaxially into andinteriorly along the jet stream 50, which stream is desirably rathershort. As explainedby Noyce, there exists a critical relationshipbetween the radiation-transmitting characteristics of the electrolyticjet liquid and those of germanium; -and the use of this relationshipwill here be described, although the situation is somewhat differentwhen light control is applied to the etching of silicone or the like. jj

When the material in the blank 10 has been reduced in thickness to acertain extent, there results a substantial transmission of light ofcertain wavelengths, so that a beam 66 begins to pass through'the blank10. This latter beam is intercepted by a photosensitive element 67having conductors 68, 62 to actuate equipment for the control of theelectrolytic process, for instance as shown by Noyce. I

A duct 79 is-shown as coaxially surrounding the cell 67. This duct issupplied with dry gas, for instance dry air, through inlet means 71,said gas being directed through a nozzle 72 at the end of the duct 70and there 'by against an area of the blank 10 opposite the impingementarea of the jet 50; It has been "found that such drying of the back ofthe blank sensibly improves the precision etching by eliminating orreducing noise which otherwise disturbs the infrared control signal.Excess air from nozzle 72 may be vented off from the housing 58 by ventmeans 73, even if the *aspirators are not operating,.whereas accumulatedliquid or humidity, not intercepted by the aspirators, may be withdrawnby a drain 74.

The greatly enlarged diagram of Figure 8 shows how the fine je't'50impinges on a.solid surface area smaller than the original cavity 16 andhow it causes further etching of the impingement area, thereby reducingthe central surface barrier portion 17 of the semiconductive body '10 toa minute thickness, with a surface 75 spaced from the opposite cavitysurface by not more than a thin laminap This -film may have for instancean ultimate thickness such as .02 to .2 mil.

In processes of the present type, employing an electrolytic jet stream,the etched cavity tends to have a surface of the approximate form of aconcave spherical segment. As a result, the solid body 10 forms adiverging lens for such'radiation as it transmits. This is indicated 'bythe diverging form of the beam 66, bounded by outer rays 76, 77. As theprecision etching progresses and the surface 75 is more deeply etchedinto the semi-conductor tially increased tothe same extent'as thediverging effect.

As a result, the photocell 67 (Figure 6) receives progressively reducedillumination, as the precision etching progresses; and correspondingly,the circuit 68, 69,

- tensity of radiation at certain wavelengths, begins to reach thephotocell.

This now causes a rise in potential in the photocell output circuit.When this change-over from gradually falling to rising photocellpotentials has been initiated or established, the precision etching can"be manually-or automatically terminated.

In addition to the light beam 64, employed for the afore-mentionedcontrol purposes, a lateral beam of light 82 may be directed onto thejet impingement area, from a strong red or white or similar lightsource, not shown. Strong illumination of the semiconductor hassignificant effects upon the etching process itself; it accelerates thisprocess and sharpens the contours of the etched areas, as is known fromsaid Tiley-Williams application.

In accordance with the present invention it is import ant ,to note thefact that the exact configuration of the liquid stream 50, particularlyin the impingement portion 83, has certain effects upon the optical orequivalent processes connected with the illumination by the light beams64, 82. The critical intensity of the illumination reaching thephotocell, upon. predetermined thinning of the solid film 17, is largelydependent upon the optical characteristics of the medium through whichthe light passes; and the transition portion 83 of the liquid body is ofparticular significance in this respect. Assuming for instance that thecohesive forces of the electrolyte liquid are allowed to change thisportion 83, together with ,the outflow portion 84 surrounding the same,into an incipient liquid ball 85; this would lead to considerablescattering of light from the incident beam 64, due to the presence ofunavoidable eddies in the liquid, among other things; and the scatteringeffect would vary if a larger liquid ball 85' were gradually formed. Thescattered light would be deflected along paths such as thoseschematically shown at 86, 87.

By contrast, so long as the column 50 retains a uniform, smooth,columnar shape, as shown, the outer boundaries thereof apply a constantlight-guiding effect, thereby preventing the scattering and theirregularities thereof. It is therefore important for the illuminationin general and mainly for the infrared control process to avoidirregularities such as those shown at 85, 86, 87.

It is desirable also to avoid any serious irregularity in theapplication of the lateral light 82; for instance, care should be takento avoid the passage of liquid droplets '88 through the beam of laterallight, since the lens effects of such droplets could seriously disturbthe illumination of the impingement area.

The controlled illumination obtained in this way improves also theeffect of the electrolytic currents, basical- 1y described above andwhich is one of the important elements of the precision etching as wellas of other electrolytic operations according to this invention. Iflight were caused by droplets or the like to reach all or differentparts of the impingement area with variable intensity, this would leadto substantial variations of the electrolytic processes, aside from thediffusion of the electrolytic currents by the balling-up of the liquid.Thus the simple pneumatic-hydraulic device or method of the presentinvention improves not only the process of infrared wave control appliedto a semi-conductor, it also improves, in several ways, the process ofapplying electrolytic currents to semiconductors and other materials.

While two embodiments of the invention have been described, it should beunderstood that the details thereof are not to be construed aslimitative of the invention, except insofar as is consistent wtih thescope of the following claims.

I claim:

1. In a process of jet-electrolytic treatment of a semiconductor,maintaining a fine, coherent jet column of electrolyte liquid directedtoward the semiconductor, which column tends to form a single, cohesiveliquid ball, coaxial with said jet, larger than the diameter of saidjet, and adherent on the semiconductor; counteracting such forming ofliquid balls by applying suction to the atmosphere surrounding the jet;and applying sufficient electrical potential between jet liquid andsemiconductor to accomplish said treatment.

2. In the fabrication of transistors and the like: holding a small bodyof semiconductive material, exposed in a gaseous atmosphere; maintainingan electrolyte liquid jet carrying an electrical current, traversingsaid atmosphere and ending in an impingement area on said body, forjet-electrolytic treatment of said body in said area, followed bypassage of the liquid away from said area; the size and condition of thejet and of the impingement area being such that liquid from the jettends to accumulate'as a single coherent liquid droplet adherent to theimpingement area on the semiconductive body, coaxially with the jet,which droplet would, on continued maintenance of the jet without othertreatmentof the liquid, grow into a coherent and adherent drop, largerthan the diameter of the impingement area and interfering with saidtreatment; and counteracting the cohesion of the impinging liquid whileleaving such liquid adherent to the impingement area by aspirating acurrent of gas over said impingement area.

3. A method of fabricating transistors and the like comprising the stepsof: maintaining a jet column of aqueous electrolyte liquid, with an endportion of said column contacting a minute surface portion of a smallbody of semiconductive material, while limiting the diameters of saidcolumn and surface portion to a few thousandths of an inch; preventingthe liquid of the column, in said region, from balling up on saidsemiconductive body into a liquid drop larger than said minute surfaceportion by drawing a current of gas over and from the region of contactbetween said liquid column and said semiconductive body; and passingelectrolytic current through said liquid column and said semiconductivebody, for electrolytic treatment of the latter.

4. In the treatment of transistor material and the like by ajet-electrolytic method wherein a minutely thin jet column of liquidelectrolyte, carrying an electrical current, impinges against asemiconductive body and tends to adhere thereto, the improvement whichcomprises: counteracting cohesion of the liquid, and there by preventingaccumulation of a coherent liquid body, which otherwise would accumulatein the form of a single drop surrounding the end of the liquid column onthe semiconductive body, by maintaining a pressure gradient in theatmosphere overlying the minute area of impingement of the liquidcolumn.

5. In a method as described in claim 4, passing radiation through thearea of liquid impingement, for aiding said treatment of thesemiconductive body, while maintaining said pressure differential.

6. In a method as described in claim 4, passing a beam of radiationthrough the area of liquid impingement, for controlling the progress oftreatment of the semiconductive body, while maintaining said pressuredifferential.

7. In a method as described in claim 6, passing said beam longitudinallythrough said column.

References Cited in the file of this patent UNITED STATES PATENTS1,114,592 De \Vitt Oct. 20, 1914 1,654,727 Green et al. Jan. 3, 19281,814,866 Stride July 14, 1931 1,982,345 Kirby Nov. 27, 1934 2,523,018Henderson Sept. 19, 1950 2,568,803 Guenst Sept. 25, 1951 FOREIGN PATENTS335,003 Great Britain Sept. 8, 1930 OTHER REFERENCES Proc. of theI.R.E., December 1953, pp. 1706-1708, by Tiley et al.

1. IN A PROCESS OF JET-ELECTROLYTIC TREATMENT OF A SEMICONDUCTOR, MAINTAINING A FINE, COHERENT JET COLUMN OF ELECTROLYTE LIQUID DIRECTED TOWARD THE SEMICONDUCTOR, WHICH COLUMN TENDS TO FORM A SINGLE, COHESIVE LIQUID BALL, COAXIAL WITH SAID JET, LARGER THAN THE DIAMETER OF SAID JET, AND ADHERENT ON THE SEMICONDUCTOR, COUNTERACTING SUCH FORMING OF LIQUID BALLS BY APPLYING SUCTION TO THE ATMOSPHERE SURROUNDING THE JET, AND APPLYING SUFFICIENT ELECTRICAL POTENTIAL BETWEEN JET LIQUID AND SEMICONDUCTOR TO ACCOMPLISH AND TREATMENT. 